Method of applying an aminopyridine compound to soil and the product thereof to prevent nitrification in soil



dues, organic fertilizers or bacterial syntheses.

United States Patent C) 3,050,382 METHOD OF APPLYENG AN GPYREEH TJ COMPUUND T SUE AND THE PRODUCT gggREOF TO PREVENT PICATION lN Cleve A. I. Goring, Garden Grove, (Ialii, assignor to The Dow Chemical Company, Midland, Mich, a corporation of Delaware No Drawing. Filed Apr. 16, 1957, Ser. No. 653,9d7 13 (Ilaims. (Cl. 71-1) The present invention relates to crop culture and is particularly concerned with a new agronomical practice and composition for conserving soil nitrogen and for supplying the soil nitrogen requirements for plant nutrition.

Since the majority of plants obtain most or all of their nitrogen requirements from the soil, the adequate provision of nutrient nitrogen in soil for plant growth is one of the foremost agronomic problems. The nitrogen in the soil is found to occur primarily in three forms: organic nitrogen, ammonium nitrogen and nitrate nitrogen, of which ammonium nitrogen and nitrate nitrogen are the primary forms utilized by plants. This nitrogen is absorbed by plants in solution from the soil in the form of ammonium ions and nitrate ions.

The organic nitrogen in the soil consists of a large number of compounds and originates from manure, crop resi- Since with the exception of the organic reduced nitrogen fertilizers such as urea, the solubility of these compounds in water is very low, they are not readily leached from the soil, but neither are they directly available to the plants for use. In order to be available to the plants,-the nitrogen in the organic compounds must be converted by soil bacteria to ammonia or inorganic ammonium salts. This conversion, when from organic reduced nitrogen fertilizers such as urea, takes place very rapidly, but very slowly when from other organic nitrogen compounds. Following the conversion, the ammonium nitrogen is very rapidly oxidized by soil bacteria to inorganic nitrate nitrogen. In this process, the ammonium nitrogen is first oxidizedto the intermediate nitrite nitrogen which is then rapidly oxidized to nitrate nitrogen. This mineralization of organic nitrogen constantly replenishes the soil with nitrogen available for plant absorption.

The ammonium nitrogen in the soil is derived from bacterial conversion of organic nitrogen or from the added reduced nitrogen fertilizers such as anhydrous ammonia, aqueous ammonia, ammonium phosphate, ammonium nitrate and ammonium sulfate. These ammonium compounds or inorganic reduced nitrogen compounds are readily soluble in water or aqueous soil medium. When .in solution, the reduced nitrogen occurs largely as the ammonium ion. Due to the cationic nature of this ion, the ion is strongly adsorbed on the soil colloids or base exchange complex of the soil. This colloidal-bound ammonium nitrogen exists in equilibrium with a small concentration of ammonium ions in the soil solution. Thus, the colloidal-bound ammonium nitrogen provides a dynamic nitrogen reservoir to maintain a supply of ammonium ions in the soil solution for plant adsorption. Further, since the ammonium nitrogen in the soil occurs principally as colloidal-bound nitrogen, only very small quantities of the ammonium form of soil nitrogen are lost from the feeding zone of the plants by leaching.

The nitrate nitrogen in the soil is derived from the oxidation or nitrification of ammonium nitrogen by soil bacteria, or by the addition of inorganic nitrate fertilizers such as ammonium nitrate, sodium nitrate, potassium nitrate and calcium nitrate. The inorganic nitrate compounds are readily soluble in water and the aqueous soil medium. When so dissolved, the nitrate nitrogen lar ely exists as the nitrate ion. Because of the anionic nature of ice this ion, nitrate nitrogen is rapidly leached by rainfall and irrigation and readily lost from the feeding zone of the plants. Further, the nitrate nitrogen is reduced by many soil bacteria to nitrogen gas. The'latter process is known as denitrification and accounts for an additional loss of large quantities of nitrate nitrogen hom the soil. The yearly loss from leaching and denitrification amounts to from to 80 percent of the nitrate nitrogen found in the soil, whatever its source.

Nitrification or the conversion of the ammonium nitrogen in soil to nitrate nitrogen by bacterial action occurs at a rate which is dependent primarily upon the soil temperature and the soil pH. The rate is also somewhat dependent upon the type of soil and the moisture content of the soil. The rate of nitrification is rapid when the soil temperature is at least 10 C. and the soil pH is at least 5. For example, the conversion of ammonium nitrogen to nitrate nitrogen in sand, silt or clay loam soil having a pH of at least 6 may take place at a rate of from 20 pounds of nitrate nitrogen per acre per week at 10 C., to 500 pounds of nitrate nitrogen per acre per week at 35 C. Even at temperatures as low as 2 C., nitrification will oftentimes occur in such soils at a rate of pounds of nitrate nitrogen per month. Thus, ammonium nitrogen is very rapidly changed to nitrate nitrogen in most agricultural soils.

The tremendous losses of soil nitrogen resulting from the rapid nitrification of ammonium nitrogen, and the leaching and bacterial'decomposition of nitrate nitrogen have depleted many agricultural soils of the nitrogen reserves and nitrogen requirements for plant nutrition. In order to replenish the soil nitrogen, the agriculturalist has resorted to the use of large amounts of nitrate fertilizers and reduced nitrogen fertilizers. In many instances, multiple fertilizer treatments during the growing season have been required to maintain adequate nitrogen requirements for plant growth. In this practice, the greater proportion of the employed fertilizers is in the form of reduced nitrogen fertilizers. By the expression reduced nitrogen fertilizers is meant fertilizers containing nitrogen in the reduced state and is inclusive of ammonium salts, ammonia, and water-soluble organic compounds readily convertible in soil to ammonia or ammonium ions such as urea and cyanamide.

Since the nitrogen must be present as nitrate nitrogen before substantial quantities can be leached from the soil or lost by denitrification, the application of nitrogen as reduced nitrogen fertilizers provides the agriculturalist with ashort interval during which available reduced nitrogen is at a maximum and conditions for leaching and denitrification are at a minimum. This interval is particularly advantageous during the initial growth of seeds and emerging seedlings when high soil nitrogen concentrations are very desirable. In addition, the ammonium nitrogen absorbed by plants is immediately available for assimilation into organic materials being synthesized thereby. In contrast, the nitrate nitrogen must be reduced before it can be assimilated in the synthesis of plant materials. This reduction is carried out in the plant usually at the expense of synthesized carbohydrate. Although some plants seem to do well on either ammonium nitrogen or nitrate nitrogen as a source of nitrogen nutrients, many plants such as potato, corn, rice, buckwheat, pineapple, cotton and orange prefer ammonium nitrogen and appear to grow best in the presence of substantial amounts of this form of nitrogen. Thus, the need for a method of suppressing the rapid loss of soil nitrogen is well recognized by agriculturalists.

An object of the present invention is to provide a new and improved agronomic practice for conserving soil nitrogen. A further object is the provision of a new and improved method for suppressing the loss of soil nitrogen.

. .7, V I 3 I An additional object is the provision of a new and improved method for suppressing the loss (if-ammonium nitrogen from soil. Another object is the provision of a new and improved method for supplying soil with nitrogen available for plant growth. Another object is the a provision ofa new and improved method for suppressing the loss of reduced nitrogen fertilizer supplements from I soil. An additional object is the provision of a new and improved method for suppressing the nitrification of ammonium nitrogen in soil. Another object is the provision of a new and improved method for suppressing the conversion in soil of ammonium ions to nitrate ions. An

7 additional object is the provision of novel compositions to be employed in the newv methods of the present invention. Other objects will become apparent from the following specification and claims.

The new agronomical practice for improving plant nutrition and conserving soil nitrogen comprises treating 'plant growth media with an aminopyridine compound comprising (1) aminopyridines having the formula wherein X represents hydrogen or methyl and Y represents hydrogen, chlorine or bromine, and (2) salts of said aminopyridines. Suitable salts include hydrochlorides, hydrobro-mides, sulfates, phosphates, citrates, oxa-.

lates, acetates, tartrates, formates and carbonates. The

aminopyridine compounds are generally solid materials adapted to be readily and conveniently distributed in soil.

1 By the practice of this invention, the ni'trification of ammonium nitrogen inthe soil to nitrate nitrogen is suppressed thereby preventing the rapid loss of ammonium nitrogen from the soil. Furthermore, by proper distribution of the aminopyridine compound, this "action of inhibiting the transformation of ammonium nitrogen to nitrate nitroge'n'is efiective over a prolonged period of time. The'ammonium nitrogen may arise from added ammonium nitrogen fertilizers or be formed in the soil by conversion of the organic nitrogen constituents found 7 in soil or added thereto as components of organic fertilizers. V

Theprovision of an effective dosage of the aminopyridines in the soil or growth medium is essential for the practice of the present invention. In general, good results 'are obtained when the growth medium is modified a with the aminopyn'dine in the amount of from 2 to 150 partsor more by weight of the latter per million parts by weight of growth medium. In field applications, the aminopyridine compound may be distributed in the soil in the amount of at least 0.5 pound per acre and through such a cross section of the soil as to provide for the presence'therein of an eifective concentration of the agent. It is usually preferred that/the aminopyridine compound be distributed to a depth of at least two inches below the soilsurface 'and at a dosage of at least 0.7 pound per" acre inch of soil. By dispersing very large dosages in growth*media, a prolonged inhibition of nitrification may be obtained over a period of many months.

i V The concentration of the active aminopyridine compound is eventually' reduced to a minimum by decomposition in thesoil. V 7

1 In one embodiment of the present invention, the aminosublethal to plantgrowth' In such operations, the aminopyridine compound should be supplied in the soil in an amount no" greater than about 50 parts by Weight .per

million parts by weight of the soil. By following such Jpractice, no adverse effect is exerted by the aminopyridine compound may vary from 0.001 percent by weight to 95 a I compound upon growth of seeds or plants. Oftentimes it is desirable to treat the soil adjacent to plants, and this 7 procedure may be carried out conveniently in side-dressing operations. i

in a further embodiment, soil may be treated with the aminopyridine compound following harvest or after fallowing to prevent rapid loss of ammonium nitrogen and to build up the ammonium nitrogen formed by conversion of organic nitrogen compounds. Such practice conserves the soil nitrogen for the following growing season. 7

In an additional embodiment, the soil is treated with the aminopyridine compound in conjunction with the application of reduced nitrogen fertilizers. The treatment with the aminopyridine compound may be carried out prior to, subsequent to or simultaneously with the application of fertilizers. Such practice prevents the rapid -loss or". the ammonium nitrogen added as fertilizer and the ammonium nitrogen formed from the organic reduced nitrogen in fertilizers by the action of soil bacteria. The administration to the soil of the aminopyridine compound as a constituent of an ammonium nitrogen fertilizer composition constitutes a preferred embodiment of the pres- V ent invention.

The present invention maybe carried out by distributing the aminopyridine compound in an unmodified form through growth medium. The present method also embraces distributing tthe compound as a constituent in liquid or finely divided solid compositions. In such practice, the aminopyridine compound may be modificdwith one or more addita-ments or soil treating adjuvants including water, petroleum distillates or other liquid carriers, sur-.

face-active dispersing agents, finely divided inert solids and nitrogen fertilizers. Depending upon the concentration of the aminopyridine compound, such augmented composition may be distributed in the soil without further 1 modification or be considered a concentrate and subse-.

quently diluted with additional inert carrierto produce the ultimate treating composition. The required amount of the aminopyridine compound may be supplied to growth media in from 1 to gallons of organic solvent carrier, in from 5 to 27,000 or more gallons of aqueous carrier, or in from about 20 to 2,000 pounds of solid carrier per acre treated. When -an organic solvent carrier is employed, it may be further dispersed in the above volume of aqueous liquid carrier.

The concentration of theaminopyridine compound in compositions to be employed for the treatment of growth media is not critical and may vary considerably provided I the required dosage of effective'agent is supplied to the growth media. The concentration of the aminopyr-idine percent by weight of the composition, depending on whether the composition is a treating composition or a concentrate composition .andwhether it is in the form of a solid or a liquid. In aqueous liquid treatirrgcompositions, concentrations of'from 0.001 percent to 0.25 percent by weight of aminopyridine compound is considered the preferred composition. The concentration of the aminopyridine compound in organic solvents may ;be from 2.0 to 50 percent by weight. Concentrate liquid compositions generallygcontain from. 2.5 to 50 percent by weight of the aminopyridine compound. Solid compositions may contain the aminopyridine compound in amounts as high as percent by weight of the active compound. Treating "compositions generally contain 0.004 percent to 10 percent by weight of the'aminopyridine compound. Concentrate compositions oftentimes may contain from 2.5 to 95 percent of the aminopyridine' compound.

Liquid compositions containing the desired amount of the aminopyriidine compoundmay be prepared by dispersingthe latter in one or more liquid carriers such as water or an organic solvent, with or without the aid'of a suitable surface-active dispersing agent or emulsifying agent. Suitable organic solvents include acetone, diisobutylketone, methanol, ethanol, isopropyl alcohol, diethyl ether, toluene, methylene chloride, chlorobenzene and the petroleum distillates. The preferred organic solvents are those which are of such volatility that they leave little permanent residue in the soil. When the solutions of the aminopyridine compound in organic solvents are to be further diluted to produce aqueous dispersions, the preferred solvents include acetone and the alcohols. When the liquid carrier is entirely organic in nature, particularly desirable carriers are the petroleum distillates boiling almost entirely under 400 F. at atmospheric pressure and having a flash point above about 80 F. Dispersing and emulsifying agents which may be employed in liquid compositions include condensation products of alkylene oxides with phenols and organic acids, alkyl aryl sulfonates, polyoxyalkylene derivatives of sorbitan esters, complex ether alcohols, mahogany soaps and the like. The surface-active agents are generally employed in the amount of from 1 to 20 percent by weight of the aminopyridine compound.

Solid compositions containing the active aminopyridine compound may be prepared by dispersing the compounds in finely divided inert solid carriers such as talc, chalk, gypsum, vermiculite, bentonite and the like, fullers earth, attapulgite and other clays, various solid detergent dispersing agents and solid fertilizer compositions. In preparing such compositions, the carrier is mechanically ground with the aminopyridine compound or wet with a solution or dispersion thereof in a volatile organic solvent. Depending upon the proportions of ingredients, these compositions may be employed without further modification or be considered concentrates and subsequently further diluted with solid surface-active dispersing agent, talc, chalk, gypsum or the like to obtain the desired treating composition. Furthermore, such concentrate compositions may be dispersed in Water With or without added dispersing agent or agents to prepare aqueous soil treating compositions.

Soil treatment compositions may be prepared by dispersing the aminopyridine compound in fertilizers such as ammonium fertilizer or organic nitrogen fertilizer. The resulting fertilizer composition may be employed as such or may be modified as by dilution with additional nitrogen fertilizer or with inert solid carrier to obtain a composition containing the desired amount of active agent for treatment of soil. Further, an aqueous dispersion of the aminopyridine compound-fentilizer composition may be prepared and administered to the growth medium. Fertilizer compositions comprising the aminopyridine compound in intimate admixture with ammonium fertilizers constitute preferred embodiments of the present invention.

In fertilizer compositions comprising a reduced nitrogen fertilizer, it is desirable that the aminopyridine compound be present in an amount of at least 0.5 percent by weight based on the weight of the nitrogen present in the fertilizer as reduced nitrogen. Thus, when a fertilizer cornposition contains both reduced nitrogen and other forms of nitrogen such as in the case of ammonium nitrate fertilizer compositions, the amount of aminopyridine compound is based on the weight of nitrogen present in the ammonium component.

In operations carried out in accordance with the present invention, the soil may be impregnated in any convenient fashion with the aminopyridine compound or a composition containing the latter. For example, these modified or unmodified compositions may be mechanically mixed with the soil; applied to the surface of soil and thereafter dragged or disced into the soil to a desired depth; or transported into the soil with a liquid carrier such as by injection, spraying or irrigation. When the distribution is carried out by introducing the aminopyridine compound in the water employed to irrigate the soil,

the amount of water is varied in accordance with the moisture content of the soil in order to obtain a distribution of the aminopyridine compound to the desired depth. The aminopyridine compound may be readily and conveniently distributed to a depth of from two to four feet by irrigation methods. The preferred methods embrace procedures using any of these steps or combination of steps wherein the aminopyridine compound is distributed in the soil substantially simultaneously with a reduced nitrogen fertilizer.

The following examples illustrate the invention but are not to be construed as EXAlVIPLE 1 An aqueous ammonium fertilizer composition containin 1,000 parts by weight of nitrogen and 50 parts by Weight of 2-amino-5-chloro-3-picoline per million parts of aqueous medium was prepared by dispersing a 4 per cent (weight by volume of solvent) acetone solution of Z-amino-S-chloro-S-picoline in aqueous ammonium sulfate solution. (The amount of nitrogen in all examples is based on the nitrogen present in the fertilizer in the reduced form.)

The composition so prepared was employed to treat seed beds of sandy loam soil having a pH of about 8, containing essentially no organic material and having been freed of nitrite and nitrate nitrogen by prior thorough leaching with water. in the treating operation, the composition Was applied to the seed beds of a soil drench, and the soil in the beds thoroughly mixed to insure a substantially uniform distribution of the composition throughout the soil. The amount of composition employed was sufilcient to supply 200 parts by weight of nitrogen and 10 parts by weight of 2-amino-S-chloro-S-pic-oline' per million parts by weight of soil. In a check operation,

other seed beds similarly prepared were fertilized with a similar aqueous fertilizer composition containing the same amount of acetone and ammonium sulfate but no 2-arnino-5-chloro-3-picoline. The composition was applied in an amount to supply the same concentration of nitrogen to the soil as the treating composition containing 2-amino-5-chloro-3-picoline. The soil temperature of all seed beds was maintained at about 70 F for the period of the determination.

At various intervals following treatment, samples of soil were taken from different seed beds and the extent of nitrification of the added ammonium sulfate fertilizer determined by analyses for combined nitrate plus nitrite nitrogen. The determinations were carried out by extracting the nitrate and nitrite from the soil with a saturated calcium sulfate solution, developing color in the clear supernatant of the extract with diphenylamine in sulfuric acid, and comparing the color with a standard solution containing known concentrations of nitrate and nitrite ions. This procedure is similar to that described in C01- orimetric Methods of Analysis by F. D. Snell and C. T. Snell, D. Van Norstrand Company, Inc., volume II, 3rd edition, page 801.

The percent nitrification in the seed beds of the added 7 v p 7 VEXAMP LE- 2 V Ane'xperiment was carried out in a manner similar to that described in Example 1 but wherein the final concentrations of the 2-amino-5-chloro-3-picoline and the am- 7 moniuni nitrogen were reduced. An aqueous ammonium fertilizer composition containing 500 parts by weight of nitrogen and 25 parts by weight of 2-amino-5-chloro-3- picoline per million parts of aqueous medium was prepared by dispersing a 2 percent (weight by volume of solvent) acetone solution of 2-amino-5-chloro-3-picoline in aqueous ammonium sulfate solution. The composition was applied to soil beds in an amount sufiicient to give a concentration of the 2-amino-5-chloro-3-picoline therein of 5 parts by weight and of nitrogen of 100 parts by weight per million parts by Weight of soil. The degree of nitrification was determined after intervals of 7 days and 14 days and found to be percent and 15 percent, respectively. A check operation carried out with a composition containing no 2arnino-S-chloro-3-picoline showed 100 percent nitrification at both intervals.

EXAMPLE 3 7 An experiment was carried out in a manner similar to that described in Example 2 but wherein 2-amin'o-3-picoline-dihydrochlon'de was substituted for Z-amino-S-chloro-3-picoline and'the final concentrations of the amino- 7 pyridine compound and nitrogen in the soil were parts by weight and 100 parts by weight per million parts by weight of soil, respectively. The degree of nitrification was determined after intervals of 7 and 14 days and found 7 t to be and percent, respectively. A check operation carried out with a composition containing no 2-amino-3- picoline-dihidrochloride showed 100 percent nitrification at both intervals.

' EXAMPLE 4 Ammonium sulfatetand an acetone solution containing 4 percent (weight by volume of solvent) of 3-aminopyridine were dispersed in water to prepare an aqueous V composition containing 1,000 parts by weight of nitrogen and parts by weight of 3-aminopyridine per million parts by weight of ultimate mixture. This composition was applied to seed beds of sandy loam soil similar to a that described in Example 1, in an amount'sufiicient to provide 200 parts by weight of nitrogen and 10' parts by weight of 3-aminopyridine per million parts by weight of a soil.

on other seed beds employing a similar aqueous fertilizer composition but containing no 3-aminopyridine.

At various intervals following treatment, analyses were 'made on samples of soil from the different seed beds for A check'operation was simultaneously carried out their content of nitrite plus nitrate nitrogen and the per- 7 'cent nitrification of ammonium sulfate determined thereby; The percentage nitrification at various intervals is Aqueous ammonium sulfate compositions varying; in

the aminopyridine' component were prepared in a inanrnersimilar to that described in Example 1 and applied I to seed beds of s andy loam soil'having a pI-l of about 8,

' lizer compositions containing 5 percent by weightof an as previously described, in amounts suflicient to supply 200 parts by weight of nitrogen and 10 parts by weight of" the aminopyridine per million parts by weight of soil.- Check operations were carried out simultaneously on seed beds of similar soil employing an aqueous fertilizer composition in which the aminopyridine was omitted.

At various intervals following treatment, samples of soil from the different seed beds were analyzed for their content of nitrite plus nitrate nitrogen and the percent nitrification of ammonium sulfate determined. The soil treating compositions employed and the percentage nitrification at the various observation intervals are set forth in TablejIII.

Table III Interval Percent Treating Composition 'Following Nitrifica- Treatment 7 tion in Days Ammonium sulfate 2-aminopyridine 6 5 Ammonium sulfate (check) 6 r 100' Ammonium sulfate itaminopyridineu Ammonium sulfate (check) 27 100 Ammonium sulfate 6-amin0-2-picoline 6 5 Ammonium sulfatefoheek) 6 ,100 Ammonium sulfate 6-amino-2-picolin 20 8 7 Ammonium sulfate (check) 20 100 Ammonium sulfate 6-amino-2-pico 27 -10 Ammonium sulfate (check) 27 100 Ammonium sulfate 2-amino-4-picoline Ammonium sulfate (check) 27 100 Ammonium sulfate 2-amino-3-picoliue 13 10 Ammonium sulfate (check) 13 100 Ammonium sulfate 2-amino-3- 27 15 Ammonium sulfate (check) 27 100 Ammonium sulfate 2rami picoline 27 10 Ammonium sulfate (check) 27 100 Ammonium sulfate 2 amino-fi-bromo-3- picoline l3 10 Ammonium sulfate (cheek) 13 100 EXAMPLE 6 Concentrate compositions are prepared as follows: (A) 25 parts by weightof 2-amino-6-bromopyridine', parts of xylene and 10 parts of an alkylated aryl polyether alcohol (Triton X-lOO) are mechanically mixed together to obtain an emulsifiable liquid compositiong (B) parts by weight of 2-amino-6-chloropyridine and :10 parts of an alkyl aryl sulfonate (Acto 700) 'are mechanically mixed together to obtain a water-dispersible mixture. 7 V j These compositions may be dispersed in water to produce aqueous compositions having desirable wetting and penetrating properties. then employed to treat soil in an amount sufiicient to distribute the aminopyridine compounds therein in effective concentrations. The concentrates may also be dispersed in aqua ammonia to prepare fertilizer compositions.

EXAMPLE 7 Fertilizer compositions are prepared as follows: 7

(A) Mono and dihydrobromide salts of 2-aminopyri-' dine are mechanically mixed in separate portions with diammonium phosphate to prepare reduced nitrogen fertiaminopyrldine compound.

(B) Mono and dinitrate salts of 6-amino-2-picoline and 2-amino-3-bromo-2-picoline are mechanicallymixed with ammonium nitrate to prepare reduced nitrogen fertilizer compositions containing3 percent by weight of one of the salt compounds. a

(C) Mixed phosphates of Z-amino-S-chloro-Z-picolihe are mechanically'mixed with urea to prepare reduced nitrogen fertilizer compositions containing .2 percent by weight of the phosphate salts. 1. a f

.These fertilizer compositions are distributed in soil to supply the nitrogen requirements'for plant nutrition 'The treated soil is resistant to nitrification and provides nitro These aqueous compositions are 9 gen available for plant growth over a prolonged period of time.

EXAMPLE 8 Aqueous ammonium fertilizer compositions containing 1,000 parts by weight of nitrogen and 50 parts by weight of 3-aminopyridine in a million parts of aqueous media were prepared by dispersing an acetone solution containing 4 percent (weight by volume of solvent) of 3-aminopyridine in aqueous solutions of various ammonium compounds.

In an operation similar to that described in Example 1, the soil in seed beds was treated with the above described compositions to distribute a particular composition throughout the soil in an amount sufiicient to supply a concentration of nitrogen in the soil of 200 parts by weight and of S-aminopyridine of parts by weight per million parts by weight of soil. The treated soil was maintained at 70 F. for the period of the determination. At various intervals, samples of the soil were taken and analyses made to determine the extent of nitrification.

Soils treated with the ammonium phosphates and aqua ammonia were analyzed for nitrate plus nitrite nitrogen as previously described. The soils treated with ammonium nitrate were analyzed for residual ammonia by extracting the soil with 2 molar potassium chloride and the ammonia in the extract determined by comparisons with a standard on a spot plate using Nesslers reagent as indicator.

Check operations were simultaneously carried out on other seed beds employing similar aqueous fertilizer compositions but containing no 3-aminopyridine. The results of the treating and check operations are given in Table IV.

Table IV Percent Nitrification Treating Composition Ammonium nitrate S-aminopyridine Ammonium nitrate (check) Ammonium nitrate 3-aminopyridine Ammonium nitrate (check) Ammonium nitrate 3-aminopyridin Ammonium nitrate (check) Aqua ammonia .S-aminopyridine- Aqua ammonia (check) Aqua ammonia 3-aminopyridine- Aqua. ammonia (check) Aqua ammonia 3-amiu0pyridine Aqua ammonia (check) Diammonium phosphate 3 op Diammoniurn phosphate (cheek) Diammonium phosphate 3-ammopyridine. Diammonium phosphate (check) Diammonium phosphate 3-aminopyridine Diammonium phosphate (check) Mpnoammonium phosphate 3-aminopyri- 1UP Monoammonium phosphate (check) Mpnoammonium phosphate 3-aminopyrill'l Monoammonium phosphate (check) Mpnoammonium phosphate 3-emin0pyrime Monoammonium phosphate (check) EXAMPLE 9 A solid fertilizer composition was prepared as follows: (1) an inhibitor component was prepared by (a) mixing and grinding together 0.2 gram of 2-amino-3-picoline and 0.3 gram of attapulgite, (1)) adding 1.5 grams of pyrophyllite thereto and grinding the resulting mixture until a finely powdered uniform composition was obtained; (2) a fertilizer component was prepared by hammermilling together a 50:50 mixture by weight of ammonium sulfate and pyrophyllite to obtain a fine uniform composition; (3) the inhibitor component and fertilizer component were mixed together in various ratios on a 10 roller mill to obtain a soil treating composition contain ing 10 percent Z-amino-B-picoline based on the nitrogen" in the composition. This composition was employed to fertilize beds of sandy loam soil containing essentially no organic material and having a pH of about 8. The soil employed had been previously leached to remove all nitrate and nitrite nitrogen constituents. A sufiicient amount of water was added to the various beds to give the soil in the beds 20 percent moisture content. The beds were fertilized in areas to be planted by providing depresssions and adding thereto the fertilizer treatingc'omposition and then covering the composition with soil. The amount of composition employed was suflicient to supply 160 parts by Weight of nitrogen per million parts by weight of soil. The soil was maintained in the temperature range of from 70 to F. for 22 days. At the end of this period, the soil was analyzed for content of nitrate plus nitrite nitrogen to determine the extentof nitrification of the added ammonium sulfate. The result was compared with the determination made on a check operation wherein a fertilizer composition containing no 2-amino-3-picoline was employed. The extent of nitrification in soil treated with the fertilizer composition con-.

taining inhibitor was 16 percent whereas the extent of nitrification in soil treated with the fertilizer composition containing no inhibitor was 88 percent.

EXAMPLE l0 Irrigation water is modified by adding an acetone solution containing 5 percent (weight by volume of solvent) of 2-a'mino-6-bromopyridine to give'a' concentration of the aminopyridine compound therein of 50' parts by weight in a million parts of water.

The water modified as described above is employed to irrigate dry sandy loam soil having a pH of '8 and previously leached to remove any nitrite and nitrate present. The depth of the sandy loam bed is 20-21 inches. An amount of modified water equal to 6 acre inches per acre is added and allowed to equilibrate in the soil by standing for several days. At the end of this period, samples of soil from various depths are taken. To each sample a suflicient volume of an aqueous ammonium sulfate solution containing 2,500 parts of nitrogen by weight per million parts of water is added to give a composition containing parts by weight of nitrogen per million parts of soil. The fertilized soil samples are thereafter maintained in the temperature range of from 70 to 85 F. At periodic intervals, samples of the soil are taken and analyses made on the nitrate plus nitrite nitrogen to determine the extent of nitrification.

Analyses on samples of soil at various levels on the 7th and 20th day after the start of incubation show a commercial control of nitrification at levels up to l0inches in the treated soil.

In a check operation, determinations are carried out on the various layers of soil irrigated with unmodified water. It is found in the check determinations that there is 100 percent nitrification at all depths in the soil at both intervals.

EXAMPLE .11

An aqueous soil treating composition containing 100 parts by weight of 2-amino-5-chloro-3-picoline, 1,000 parts by weight of nitrogen as ammonium sulfate and 500 parts by weight of phosphorus as phosphoric acid was prepared by dispersing a 4 percent (weight per volume of solvent) acetone solution of 2-amino-5-chloro-3- picoline into an aqueous solution of ammonium sulfate and phosphoric acid.

Pots were prepared for'planting with 500 grams of sandy loam soil having a pH of 8 and a 4 percent moisture content. 200 milliliters of the treating composition prepared as described above was poured over the soil (an amount equal to about 1 inch of liquid) to supply to the soil 2-amino-S -chloro-3-picoline in an amount suflicient'to parts by weight of soil and. a concentration of nitrogenof 400 parts per million. The treated soil was then covered with paper to reduce evaporation and maintained in they temperature range of from 70 to 80 F. 4

After'a period of six weeks, the soil in the pots was leached with '6 inches of water and thereafter planted with three species. Each pot was planted with four tomato plants, five milo plants and a thick stand of rye. After an appropriate growth interval, the tops of the plants were harvested just above ground level and weighed. The average fresh weight in grams per pot was determined at the time of harvest which was 35 days for tomato plants, 46 days for milo plants and 47 days for rye plants.

' A check operation was carried out simultaneously wherein soil in pots was similarly fertilized with a composition containing the same amount of ammonium sulfate, phosphoric, acid and acetone but no Z-amino-S- V chloro-S-picoline.

Table V Weight of Fresh Plant Tops in Grams per Pot Treating Composition EXAMPLE 12 A solid fertilizer treating composition was prepared by 1) grinding together 1.0 part by weight of 3-aminopyridine with 15 parts by weightof attapulgite, (2) mixing this mixture with 3 times its weight of pyrophyllite, and (3) mixing the resulting mixture with 9 times its weight of a 50/40 mixture of ammonium sulfate'and pyrophyllite. This treating composition contained 1.0 percent by weight of 3-aminopyridine and 50 percent by weight of ammonium sulfate.

Pots were prepared for planting with 500 grams of sandy loam soil having a pH of 8 and a 4 percent moisture content. 200milliliter's of a phosphoric acid solution containing 500'parts by weight of phosphorus per million parts of media was poured over soil. The soil was then Tomato Milo Rye Ammonium sulfate phosphoric acid 2-amino-5chloro-3-pieoline ace- 7 tone -e I 19. 5 20. 6 8. 5 Ammonium sulfate phos acetone (check) 6. 4 7. 7 4. 8

allowed to dry, Thereafter, a hole about %-1 inch deep I was made in the center of each pot, and 2 grams of the solid fertilizer treating composition prepared as described aboveiplacedtherein. The holes were closed by compressing the. soil together. The soil thus treated con 'tained 40 parts by weight of '3-aminopyridine and 400 a water and then planted with 4 tomato plants per pot. After a growing period of 48 days, the topsof the plants were harvested by cutting them ofi 'atthe ground level and the average fresh weight in grams per pot determined. v V r A check' operation' was carried out simultaneously fertilizer composition containing no 3-aminopyridine.

The average weight of the plant tops'at harvest in both the treating and check operations areset forth in Table J V wherein the soil in the pots was similarly treated with i 12 Table VI Weight of Fresh Treating Composition Tomato Plant Tops in Grams per Pot Phosphoric acid ammonium sulfate 3-aminopyridine -24. 9 Phosphoric acid ammonium sulfate (check) 11.3

I claim:

'1. A method useful for suppressing the nitrificationof V ammonium nitrogen in soil and preventing rapid loss of ammoniumrnitrogen therefrom, and improving plant nu-' trition therein which comprises impregating soil below the soil surface in the growing area thereof with an aminopyridine compound in an amount of from about 2 to parts by weight per million parts by weight of soil, wherein said aminopyridine compound is selected from the 7 group consisting (l) aminopyridines having the formula wherein X represents a member of the group consisting of hydrogen and methyl and Y represents a member of the group consisting of hydrogen, chlorine and bromine;

pyr idine compound is 6-amino-2-picoli.ne. g V

6. A method according to claim 1 wherein the aminopyridine compound is 2-amino-5-bromo-3-picoline.

7; A method according to claim 1 wherein the aminopyridine'comp-ound is added in an amount sufficient to" give a concentration in the soil of from 2 to 50 parts by weight per million parts by weight of soil. I r

8. Amethod according to claim 7 wherein the aminopyridine compound is introduced in the soil at a point 7 near the roots of the growing plants.

9. A method for treating soil to prevent rapid loss of ammonium nitrogen from soil and to inhibit the conversion therein of ammonium nitrogen to nitrate and nitrite nitrogen which comprises impregnating soil below the soil surface in the growing area thereof in an amount suflicient to inhibit nitrification therein, said amount being sufiicient to give a concentration inrsoil of at least 2 parts by weight per million parts by Weight o f soil with a composition comprising an aminopyn'dine compound in intimate admixture with a soil treating adjuvant, said aminopyridine compound being selected from the group consisting (1) aminopyriciines having the formula wherein X represents a memberof the group consisting of hydrogen and methyl and Y represents 'a member. of

the group consisting of hydrogen, chlorine andbromine and (2) salts of said aminopyridines.

10. A method according to claim 9,wherein the ad juvant isa reduced nitrogen fertilizer composition, said reduced nitrogen fertilizer being a fertilizerscontaining nitrogen in the reduced state and is selected from the group consisting of ammonium salts, ammonia, .urea'and cyanamide. V I 5 11. In the fertilization of soil with a reduced nitrogen fertilizer, the step which comprises impregnating soil below the soil surface in the growing area thereof substantially simultaneously with the reduced nitrogen fertilizer, an aminopyridine compound in an amount sufficient to suppress the nitrification of ammonium nitrogen in the soil and to prevent rapid loss of said ammonium nitrogen from soil but in an amount subleth-al to vegetative growth, said amount being suficient to give a concentration in the soil of at least 2 parts by weight per million parts by weight of soil, wherein said aminopyridine compound is selected from the group consisting (1) aminopyridines having the formula wherein X represents a member of the group consisting of hydrogen and methyl and Y represents a member of the group consisting of hydrogen, chlorine and bromine; and (2) salts of said aminopyridines; and wherein said reduced nitrogen fertilizer is a fertilizer containing nitrogen in the reduced state and is selected from the group consisting of ammonium salts, ammonia, urea and cyanamide.

12. A fertilizer composition comprising a major amount of reduced nitrogen fertilizer as source of ammonium ions and not to exceed 95 percent by weight of an aminopyridine compound; and wherein the aminopyridine compound is present in a concentration of at least 0.5 percent by weight based on the weight of reduced nitrogen present in the fertilizer, wherein said aminopyridine com- 14 pound is selected from the group consisting (1) aminopyridines having the formula U NH: N

wherein X represents a member of the group consisting of hydrogenated methyl and Y represents a member of the group consisting of hydrogen, chlorine and bromine; and (2) salts of said aminopyridines and wherein said reduced nitrogen fertilizer is a fertilizer containing nitrogen in the reduced state and is selected from the group consisting of ammonium salts, ammonia, urea and cyanamide.

13. A fertilizer composition comprising a major amount of a reduced nitrogen fertilizer as source of ammonium ions and not to exceed percent by weight of 2-aminopyridine as the aminopyridine compound, wherein said amino-pyridine compound is present in a concentration of at least 0.5 percent by weight based on the weight of the reduced nitrogen present in the fertilizer, and wherein said reduced nitrogen fertilizer is a fertilizer containing nitrogen in the reduced state and is inclusive, of ammonium salts, ammonia, urea and cyanamide.

References Cited in the file of this patent UNITED STATES PATENTS 2,314,091 Jones Mar. 16, 1943 2,372,588 Larsen et al. Mar. 27, 1945 2,427,286 Knapp et al. Sept. 9, 1947 2,460,710 Nolan et al. Feb. 1, 1949 2,735,225 Goodhue et al. Feb. 21, 1956 2,835,565 Goodhue etal. May 20, 1958 

1. A METHOD USEFUL FOR SUPPRESSING THE NITRIFICATION OF AMMONIUM NITROGEN IN SOIL AND PREVENTING RAPID LOSS OF AMMONIUM NITROGEN THEREFROM, AND IMPROVING PLANT NUTRITION THEREIN WHICH COMPRISES IMPREGNATING SOIL BELOW THE SOIL SURFACE IN THE GROWING AREA THEREOF WITH AN AMINOPYRIDINE COMPOUND IN AN AMOUNT OF FROM ABOUT 2 TO 150 PARTS BY WEIGHT PER MILLION PARTS BY WEIGHT OF SOIL, WHEREIN SAID AMINOPYRIDINE COMPOUND IS SELECTED FROM THE GROUP CONSISTING (1) AMINOPYRIDINES HAVING THE FORMULA 